System and method for valve greasing in a well tree

ABSTRACT

A technique facilitates greasing of valves on a well tree, e.g. a frac tree, according to a simple process which enables selected, individual valves to be greased when desired. In some applications, the greasing process may be automated and controlled via a greasing control system. According to an embodiment, a greasing system is connected with grease ports at a plurality of actuatable valves located in a well tree. The greasing system has a plurality of grease valves which may be associated with each of the actuatable valves, e.g. with each of the grease ports. A pump is used to pump grease to the grease valves and the grease valves are selectively actuated to open positions to provide controlled greasing of desired actuatable valves so as to remove debris from and to lubricate selected actuatable valves.

CROSS-REFERENCE TO RELATED APPLICATION

The present document is based on and claims priority to U.S. ProvisionalApplication Ser. No. 62/926,171, filed Oct. 25, 2019, which isincorporated herein by reference in its entirety.

BACKGROUND

Hydrocarbon fluids such as oil and natural gas are obtained from asubterranean geologic formation, referred to as a reservoir, by drillinga well. The well may contain at least one wellbore which extends downinto a subterranean formation below a wellhead. A frac tree may beinstalled on the wellhead and serves as a flow control structure duringstimulation jobs, e.g. fracturing jobs. The frac tree may comprisevarious actuatable valves which are used to control flow through thefrac tree. During stimulation jobs, sand and other debris can enter andaccumulate within internal cavities of the valves as pressurizedfracturing fluid passes through the valves. The accumulation of sand andother debris within the valves can cause serious damage and potentiallybreak the sealing integrity of the valves as they are actuated betweenopen and closed positions. The sand and debris may be displaced bygrease which is forced through the valve during maintenance activities.The grease also serves to lubricate moving parts inside the valve.

Conventional approaches to greasing may comprise manually connecting agrease hose to a fitting on the valve and then pumping grease throughthe valve. This approach tends to be a relatively time-consumingprocess. In other approaches, a relatively large number of grease hosesmay be connected between a manifold and multiple valves. Grease is thenpumped through the manifold and through the multiple valves. Due to thehigh pressure of the fracturing system, other activities at the samewell may be stopped during the greasing activity and this causesinterruptions to the overall stimulation operation. Additionally, themultiple grease hoses can cause tripping and tangling hazards.

SUMMARY

In general, a system and methodology are provided for facilitatinggreasing of valves on a well tree, e.g. a frac tree, according to asimple process which enables selected, individual valves to be greasedwhen desired. In some applications, the greasing process may beautomated and controlled via a greasing control system. According to anembodiment, a greasing system is connected with grease ports at aplurality of actuatable valves located in a well tree. The greasingsystem has a plurality of grease valves which may be associated witheach of the actuatable valves, e.g. with each of the grease ports. Apump is used to pump grease to the grease valves and the grease valvesare selectively actuated to open positions to provide controlledgreasing of desired actuatable valves so as to remove debris from and tolubricate the actuatable valves.

However, many modifications are possible without materially departingfrom the teachings of this disclosure. Accordingly, such modificationsare intended to be included within the scope of this disclosure asdefined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described withreference to the accompanying drawings, wherein like reference numeralsdenote like elements. It should be understood, however, that theaccompanying figures illustrate the various implementations describedherein and are not meant to limit the scope of various technologiesdescribed herein, and:

FIG. 1 is a schematic illustration of an example of a well tree, e.g. afrac tree, installed on a wellhead positioned over a well and showing aflow path for hydraulic fracturing, according to an embodiment of thedisclosure;

FIG. 2 is a schematic illustration of an example of a manual manifoldstyle greasing system coupled with a well tree, according to anembodiment of the disclosure;

FIG. 3 is a schematic illustration of an example of a controllablemanifold style greasing system coupled with a well tree, according to anembodiment of the disclosure;

FIGS. 4-6 are front, side, and top views of a well tree coupled with asingle grease line to connect a plurality of grease valves, according toan embodiment of the disclosure;

FIG. 7 is a schematic illustration of an example of instrumentation on afrac tree to run a single grease line to the tree for connecting aplurality of grease valves in a greasing system, according to anembodiment of the disclosure;

FIGS. 8-10 are front, side, and top views of a well tree coupled withdual grease lines to a plurality of grease valves, according to anembodiment of the disclosure;

FIG. 11 is a schematic illustration of an example of instrumentation ona frac tree for dual greasing implementation in a greasing system,according to an embodiment of the disclosure;

FIG. 12 is a cross-sectional schematic illustration of an actuatablevalve actuated to a first position, according to an embodiment of thedisclosure;

FIG. 13 is a cross-sectional schematic illustration of an actuatablevalve actuated to a second position, according to an embodiment of thedisclosure;

FIGS. 14 and 15 are schematic illustrations of a sensor system used todetect actuation positions of an actuatable valve, according to anembodiment of the disclosure;

FIGS. 16 and 17 are schematic illustrations of a sensor system used todetect actuation positions of an actuatable valve, including positionsof misalignment caused by debris, e.g. sand, in the actuatable valve,according to an embodiment of the disclosure;

FIG. 18 is an illustration of an example of a control system outputdisplay which provides information on actuatable valves of a well tree,according to an embodiment of the disclosure;

FIG. 19 is an illustration of an example of a control system outputdisplay which provides information, including warnings, regardingactuatable valves of a well tree, according to an embodiment of thedisclosure;

FIG. 20 is a schematic illustration of another example of a greasingsystem coupled with a well tree and utilizing both an actuatable valvecontrol system and a greasing control system, according to an embodimentof the disclosure;

FIG. 21 is a flow chart illustrating an example of a greasing procedure,according to an embodiment of the disclosure; and

FIG. 22 is a schematic representation of a wellsite having a greasingsystem with grease valves and pumps installed near fracturing treeswithin a high-pressure zone of the wellsite and a controller positionedin a safe zone, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of some embodiments of the present disclosure. However,it will be understood by those of ordinary skill in the art that thesystem and/or methodology may be practiced without these details andthat numerous variations or modifications from the described embodimentsmay be possible.

The disclosure herein generally involves a system and methodology whichfacilitate greasing of actuatable valves on a well tree, e.g. a fractree. By way of example, the actuatable valves may comprise mastervalves, swab or crown valves, pump down valves, flow back valves, orother types of actuatable valves used to control flow through the welltree. The technique described herein facilitates greasing of the variousactuatable valves according to a simple process which enables selected,individual valves to be greased when desired. In some applications, thegreasing process may be automated and controlled via a greasing controlsystem. Additionally, some embodiments employ an automated valve controlfor controlling actuation of the actuatable valves between closed andopen flow positions.

According to an embodiment, a greasing system is connected with greaseports at a plurality of actuatable valves located in a well tree. Eachactuatable valve may have a single grease port or a plurality of greaseports, e.g. two grease ports, located to facilitate flushing of debrisfrom the actuatable valve and for lubricating the valve. The greasingsystem has a plurality of grease valves which may be associated witheach of the actuatable valves, e.g. with each of the grease ports orwith selected pairs or groups of grease ports. A pump is used to pumpgrease to the grease valves and then to the selected actuatable valves.The grease valves may be selectively actuated to open positions to allowgrease flow therethrough and thus to provide controlled greasing ofdesired actuatable valves.

The greasing technique provides an efficient, cost-effective approach togreasing specific actuatable valves as needed without substantiallyinterrupting the overall stimulation/fracturing operation. For example,different types of actuatable valves located at different sections ofthe well/frac tree have different operational conditions and thusbenefit from different greasing frequencies. As an example, stimulationfluids with a high concentration of proppant flow through master valvesand manifold valves at relatively high pressure so those types of valvesbenefit from more frequent greasing compared to actuatable valves inother sections of the tree. The greasing system also may help avoid orreduce human exposure to high-pressure zones at a wellsite during valvegreasing while speeding up the valve greasing process with minimalinterruption to the overall stimulation operation. The technique alsoenables execution of individual valve greasing on an as-needed basis.The greasing system further enables enforcement of a more optimizedvalve greasing regimen by, for example, preventing an operator fromskipping greasing of certain valves.

Referring generally to FIG. 1 , an example of a well tree 30 isillustrated as installed on a wellhead 32 and showing a flow path forhydraulic fracturing as described in greater detail hereinbelow. Thewell tree 30 may be used during a stimulation operation with respect toa well 34 located below the wellhead 32. In this example, the well tree30 is a frac tree but the system and methodology described herein may beused on various types of well trees. In the illustrated example, thewell tree 30 has a flow cross 36 and a plurality of valve sections 38coupled in fluid communication with the flow cross 36. The plurality ofvalve sections 38 comprise actuatable valves 40. By way of example, theactuatable valves 40 may comprise master valves 42, swab or crown valves44, pump down valves 46, flow back valves 48, and/or other suitableactuatable valves 40. The well tree 30 also may comprise or may becoupled with a manifold section 50 having actuatable manifold valves 52which control fluid flow along flow paths to different wells.

By opening and closing various actuatable valves 40 on the well tree 30,different flow paths can be created for well stimulation operations suchas wireline perforation and hydraulic fracturing. Depending on theapplication, the actuatable valves 40 may be manually actuated valves,hydraulically actuated valves, or otherwise actuatable valves. Someembodiments may use a mixture of manually operated valves and otherwiseactuated valves. Additionally, each actuatable valve 40 may comprise atleast one grease port 54 through which grease may be pumped to cleardebris, e.g. sand, from internal valve cavities and to lubricate theactuatable valve 40.

Referring generally to FIG. 2 , a schematic illustration is provided offrac tree 30 having a plurality of grease ports 54 associated withcorresponding actuatable valves 40, e.g. one or two grease ports 54 peractuatable valve 40. Grease is supplied to the grease ports 54 and thusto the corresponding actuatable valves 40 via a greasing system 56. Inthis example, the greasing system 56 is a manual manifold style greasingsystem and comprises a grease reservoir 58 and a grease pump 60 which isfed by grease from the grease reservoir 58. The greasing system 56 alsocomprises a grease distribution network 62 connected between the greasepump 60 and the grease ports 54.

The grease network 62 comprises a plurality of grease valves 64positioned along grease flow lines 66. The grease valves 64 areactuatable to control the flow of grease to selected grease ports 54.For example, the grease valves 64 may be shifted between closed and openpositions to enable the flow of grease through selected grease ports 54and thus into selected actuatable valves 40. In some embodiments, thegrease valves 64 may be positioned in a grease distribution manifold 68.

According to some embodiments, the grease valves 64 may be manuallyoperated valves. In other embodiments, however, the grease valves 64 maybe automatically actuatable as illustrated in the controllable manifoldstyle grease system 56 illustrated in FIG. 3 . For example, the greasevalves 64 may each comprise a remotely controllable actuator 70 coupledwith a greasing control system 72. By way of example, the greasingcontrol system 72 may be a controllable manifold style control systemand may comprise a processor-based control 74, e.g. a computer typecontrol, which may be programmed or otherwise configured to control thegreasing of specific actuatable valves 40, e.g. via control lines 75. Insome embodiments, the processor-based control 74 may receive feedbackfrom various sensors, e.g. pressure sensors, to facilitate automation ofthe greasing operation based on feedback related to the individualactuatable valves 40. The processor-based control 74 may be separatedfrom the reservoir 58 and pump (or pumps) 60 while, for example, thereservoir 58 and pump (or pumps) 60 are positioned proximate the welltree 30 so that grease travels over a relatively short distance.

Referring generally to FIGS. 4-6 , an embodiment of the well tree 30 anda portion of the greasing system 56 is illustrated. In this example, asingle grease flow line 66 supplies grease to the grease network 62. Thegrease network 62 further comprises a plurality of branch flow lines 66which deliver the grease to corresponding grease valves 64 and greaseports 54. In a variety of applications, each actuatable valve 40 mayhave a plurality of grease ports 54, e.g. two grease ports asillustrated, with the corresponding number of grease valves 64 mountedat the grease ports 54.

As illustrated in FIG. 7 , some embodiments combine the greasedistribution network 62 into or onto the well tree 30 to further reducethe distance over which the grease travels during a greasing operation.Instead of using a separate, dedicated grease manifold 68, the greasemanifold (or other grease distribution network) may be integrateddirectly into or onto the well tree 30. In this embodiment and otherembodiments, the pump 60 may be an individual pump or a plurality ofpumps.

In some embodiments, a dual greasing configuration may be utilized asillustrated in FIGS. 8-11 . In this type of application, a plurality,e.g. two, grease flow lines 66 supply grease to the grease distributionnetwork 62. Additionally, the greasing system 56 utilizes a plurality ofgrease reservoirs 58, e.g. dual reservoirs, and a plurality of greasepumps 60, e.g. dual pumps. The greasing control system 72 may again beused to control the flow of grease to specific actuatable valves 40.However, the separate reservoirs 58/pumps 60 enable grease to be pumpedinto different ports 54 at the same time.

As will be appreciated from FIGS. 4-6 and 8-10 , rather than having aseparate, dedicated grease line 66 for each grease valve 64, multiplegrease valves 64 can be connected to receive grease from a shared greaseline 66. In some embodiments, a series of grease valves 64 aredaisy-chained to receive grease from a single, shared grease line 66. Inat least one embodiment, each grease valve 64 of a tree 30 is connectedin a single daisy chain to receive grease from a single grease line 66.In another embodiment, a tree 30 may include multiple daisy chains ofgrease valves 64 for distributing grease via shared grease lines 66. Insome instances, such as shown in FIGS. 5 and 6 , a pair of grease valves64 for an actuatable valve 40 can be connected (e.g., via a jumper orbranch lines) along a shared grease line 66 that serves as a grease busto other such pairs of grease valves 64 for other actuatable valves 40.

Referring generally to FIGS. 12 and 13 , the effect of debris, e.g.sand, accumulated inside an actuatable valve 40 is illustrated. In FIG.12 , the actuatable valve 40 is illustrated in an open flow position andin FIG. 13 the actuatable valve 40 has been shifted to a closed flowposition. However, full opening and full closure is blocked by debris76, e.g. sand, inside an internal cavity 78 of the valve 40. If thedebris 76 remains, excessive erosion of the valve gate or improper flowpath isolation can occur. To remove the debris 76, the correspondinggrease valve 64 may be opened so that greasing system 56 is able to pumpgrease through the internal cavity 78 for removal of the debris 76. Insome embodiments, two grease ports 54 on each valve 40 are used withseparate grease valves 64 which may be individually opened to removedebris 76 from each side of cavity 78.

According to some embodiments, a sensing system 80 may be used to detectthe lack of full valve opening or closure, e.g. to detect adeviation/misalignment in valve position from the desired valveposition. When such misalignment is detected, greasing control system 72may output a warning that a greasing operation should be implemented.According to some applications, the sensing system 80 may work incooperation with greasing control system 72 to automate the greasing anddebris removal.

By way of example, the sensing system 80 may comprise a plurality ofsensors 82, e.g. proximity sensors, positioned to detect valve movement,e.g. movement of a valve stem 83, as illustrated in FIGS. 14-17 . Whenthe debris 76 prevents the valve stem 83 from reaching its proper openor closed position (see FIGS. 16 and 17 ), the misalignment can bedetected via the sensors 82. The greasing operation for that particularactuatable valve 40 may then be implemented to remove the debris 76.After the greasing operation is performed, proper alignment is againdetected via the sensors 82 (see FIGS. 14 and 15 ) and this may becommunicated to the processor-based controller 74.

It should be noted that a variety of sensors 82 and sensor systems 80may be implemented to detect when performance of a greasing operation ona specific actuatable valve 40 is desired. In some applications, thesensor system 80 and processor-based controller 74 may be used inconcert to detect when greasing is desired and to automatically performthe greasing operation to remove debris 76 from that individual valve40.

The system and methodology described herein also enable enforcement ofvalve greasing when it is truly needed. For example, the well tree 30may utilize actuatable valves 40 which are hydraulically actuated. Inthis type of embodiment, the hydraulically actuated valves 40 are openedand closed to control desired flow paths during a given well operation,e.g. well stimulation operation. A hydraulic power unit may be part of acontrol system used to control the hydraulically actuated valves 40. Toenforce greasing of a specific valve or valves 40, an interlock may beadded to the hydraulic valve control system so as to force pausing ofhydraulic valve operation until the greasing is completed.

As illustrated in FIGS. 18 and 19 , a valve control system 84, e.g. ahydraulic valve control system, may comprise a processor-based systemhaving a display 85 which utilizes output screens to provide informationrelated to valve operation. However, the display 85 also may be used tooutput an indication, e.g. a warning, when valve operation is locked toenable and ensure greasing of a desired valve or valves 40 (see FIG. 19). By way of example, real-time valve status may be provided byproximity switches and collected in the software of valve control system84. When sensor misalignment occurs (see FIGS. 16 and 17 ), the softwareinterface can pause the normal operation of valves 40 and display asuitable warning message. At this stage, greasing of the selectedactuatable valve(s) 40 is performed and sensor alignment isreestablished so that valve operation may resume.

It should be noted that sensor misalignment may be one factor in thedecision-making regarding valve greasing. However, other monitoringapproaches may be implemented and appropriate software may be used todetermine when the interlock is applied. For example, the compositionand volume of stimulation fluid flow through certain valves 40 may bemonitored and used as an indicator of potential debris accumulationinside the valve 40. Various other types of information also may begathered to determine which actuatable valves 40 should be greased. Thisinformation can then be used to determine appropriate times for greasingspecific actuatable valves 40. In some instances, the controller 74 maydetect during well operations (or at some other inopportune time) thatgreasing of a valve 40 is desired. Rather than stopping operation toenforce greasing of the valve 40, the controller 74 may output anotification to a user and delay greasing to an appropriate time, e.g.the end of the well operation. The controller 74 may prompt a user toinitiate greasing at that later appropriate time, may apply an interlockto enforce greasing at that time, or automatically initiate greasing atthat time.

Referring generally to FIG. 20 , an embodiment is illustrated whichutilizes both greasing control system 72 and valve control system 84.This allows control over the greasing operation to be integrated withcontrol over the operation of actuatable valves 40 on well tree 30. As aresult, various automated procedures may be implemented. As describedabove, for example, the valve actuation may be temporarily stopped whilea greasing operation is performed on a given valve or valves 40, orgreasing operations may be scheduled or performed based on input fromthe valve control system 84, such as operational status of valve 40.

Pressure gauges 86 (or other types of sensors) may be used to monitorpressure in the various grease flow lines 66 via one or both of thegreasing control system 72 and valve control system 84. In someembodiments, software may be used to map a specific grease line 66 tothe grease port 54 on a corresponding actuatable valve 40. The pressureinformation and/or other gathered information enables monitoring of thegreasing operation in real time so that normal valve operation may berestored as soon as possible. Pressure monitoring, for example, enablesmonitoring of the full greasing cycle as grease is pumped through thevalve's internal cavity 78 on one or both sides of the valve 40. Duringgreasing of an actuatable valve 40, pressure within the internal cavity78 of the valve 40 can be inferred, e.g. by an operator or the controlsystem 72 or 84, from pressure in a grease line 66 supplying the greaseto the valve 40. In one embodiment, each grease port 54 has a dedicatedgrease line 66 whose pressure is monitored, e.g. by a pressure gauge 86.In another embodiment, at least some grease valves 64 are installed atgrease ports 54 and daisy-chained or otherwise connected to receivegrease via a shared grease line 66 whose pressure is monitored, e.g. bya pressure gauge 86. Pressure gauges 86 may be installed at any suitablelocations in the system. In some instances, pressure gauges 86 may beused to directly monitor pressure within internal cavities 78 of valves40.

Referring generally to FIG. 21 , a flow chart is provided to illustrateone example of a greasing operation. In this example, the appropriateactuatable valve 40 is initially selected for greasing, as representedby block 90. Then, sensor system 80 in cooperation with greasing controlsystem 72 and/or valve control system 84 determines whether theactuatable valve 40 is in an open or closed position, as represented byblock 92. If the actuatable valve 40 is in an open flow position, theappropriate grease valve 64 is actuated to enable grease flow throughthe corresponding grease port 54 to direct grease into the appropriateside of the valve internal cavity 78 as indicated by block 94. Thegrease pump 60 is then started to pump grease under pressure through thegrease network 62, as represented by block 96. However, if theactuatable valve 40 is in a closed position, a different grease valve 64is actuated to enable grease flow through the appropriate grease port 54on an opposite side of the valve internal cavity 78 as indicated byblock 98. The grease pump 60 would then be started to pump grease underpressure through the grease network 62 as once again represented byblock 96.

Regardless of which side or sides of the actuatable valve 40 receivesgrease, the grease line pressure is monitored, e.g. via a pressure gauge86 of the grease line 66 supplying the grease into the internal cavity78, to determine a pressure drop indicative of completion of thegreasing operation, as indicated by block 100. An example of a pressuremonitored via a pressure gauge 86 during greasing is generally depictedas a function of time in FIG. 20 . When grease is initially pumped intothe valve internal cavity 78, the pumped grease may be filling a voidleft by grease lost during prior operation. As the cavity 78 fills withgrease, pressure will build up in the cavity. At some point the newgrease will start to displace the old grease and the debris 76 to theother side of the cavity 78 and the pressure will start to fall again.This pressure spike as pressure builds up and then drops is generallydepicted by the upward and downward slopes of peak 88 in FIG. 20 . Oncethe appropriate pressure drop is determined via, for example, greasingcontrol system 72, the actuatable valve 40 may be cycled (i.e.,alternated between open and closed positions) to displacedebris-entrained grease and the corresponding grease valve 64 may thenbe closed to block further flow of grease through the correspondinggrease port 54, as indicated by block 102. The grease pump 60 may thenbe stopped, as indicated by block 104.

Assuming the actuatable valve 40 has two grease ports 54, theappropriate grease valve 64 may then be actuated to open flow of greaseto the valve internal cavity 78 on the other side of the valve gate, asindicated by block 106. The grease pump 60 would then be started to pumpgrease under pressure through the grease network 62 as represented byblock 108. The pressure of the grease is again monitored until theappropriate pressure drop is determined, as indicated by block 110.After this pressure drop, the actuatable valve 40 may be cycled todisplace debris-entrained grease and the corresponding grease valve 64is then closed to block further flow of grease through the correspondinggrease port 54, as indicated by block 112. At this stage, both sides ofthe selected actuatable valve 40 have been greased and the grease pump60 may be stopped, as indicated by block 114. In at least someinstances, the cycling of valve 40 and closing of grease valve 64 ofblocks 102 and 112 are automatically performed (e.g., by either or bothof the greasing control system 72 or valve control system 84) withoutuser intervention in response to identification of the pressure response(i.e., spike then drop) of blocks 100 and 110. Further, other portionsof the greasing operation represented in FIG. 21 may be automated insome instances, and in at least one embodiment the entirety of thegreasing operation of FIG. 21 may be automated.

Depending on the parameters of a given stimulation operation and on theconfiguration of a given well tree 30, the actuatable valves 40, valvecontrol system 84, and greasing system 56 may have variousconfigurations. For example, the actuatable valves 40 may behydraulically actuatable, electrically actuatable, or otherwiseactuatable in response to signals provided from the valve control system84. Additionally, the greasing system 56 may utilize various types ofpumps, reservoirs, greasing valves, and control systems.

For example, greasing control system 72 may comprise various types ofcomputers or other processing systems 74 programmed to automate greasingbased on data acquired from various types of sensors systems and/ordesired greasing schedules. Similarly, the greasing control system 72may work in cooperation with valve control system 84. In someembodiments, the valve control system 84 and greasing control system 72may be part of the same processing system. For example, a computer-basedprocessing system 74 may be used to control both actuation of actuatablevalves 40 and operation of the greasing system 56. In otherapplications, however, the greasing control system 72 and the valvecontrol system 84 may be separate systems controlled by individualprocessor-based controls 74.

Referring generally to FIG. 22 , an embodiment is illustrated in whichsome greasing equipment is located within a high-pressure zone neartrees 30, while other equipment is located in a safe zone remote fromthe trees 30. More specifically, FIG. 22 depicts grease skids 122 forgreasing valves, e.g. actuatable valves 40 or 52, of the trees 30 or anassociated manifold. The depicted grease skids 122 include a grease pump60 fed by a grease reservoir 58. In some instances, a grease skid 122may include multiple grease pumps 60 or reservoirs 58.

The grease skids 122 are also shown in FIG. 22 as having grease valves64 for controlling flow of grease to the actuatable valves for the trees30. Any number of suitable grease lines may be used to connect thegrease skids 122 to the actuatable valves for the trees 30. As anexample, twenty grease lines connect each tree 30 (which may alsoinclude an associated manifold section 50, such as described above) to agrease skid 122 in FIG. 22 . This arrangement would allow flow of greaseto up to twenty grease ports 54 of the actuatable valves for each tree30 via individual grease lines 66. In other instances, however, thegrease valves 64 may be installed on the tree 30 and one or more sharedgrease lines 66 may route grease from a grease skid 122 to the tree 30.In some embodiments, each tree 30 is coupled to a grease skid 122 by asingle grease line 66. As noted above, the grease valves 64 may bedaisy-chained via a shared grease line 66 or connected to a sharedgrease line 66 serving as a grease bus. The grease skids 122 may alsoinclude measurement devices 124 (e.g., sensors) for monitoring agreasing operation. These measurement devices 124 may include one ormore of stroke counters for the grease pumps 60, level sensors for thegrease reservoirs 58, or pressure gauges 86, to name but a few examples.

A human-machine interface (HMI) control 130 is connected to the greaseskids 122 to control greasing operations. Skilled artisans willappreciate that an area surrounding a tree 30 may be considered ahigh-pressure zone or otherwise hazardous area. Well operations withinthe high-pressure zone may be stopped in some instances to enable atechnician to enter the high-pressure zone and perform certain tasks. Inthe embodiment depicted in FIG. 22 , however, the HMI control 130 ispositioned in a safe zone outside of the high-pressure zone surroundingthe trees 30 to enable user-control of the greasing operation from thesafe zone. The demarcation between the high-pressure zone and the safezone is generally represented by dashed line 132 in FIG. 22 . In oneembodiment, the HMI control 130 is an HMI control skid with aprogrammable logic controller (PLC), e.g. controller 74, placed in thesafe zone. Power may be provided from the HMI control 130 to the greaseskids 122, and communication lines facilitate communication (e.g., datasignals and command signals) between the HMI control 130 and the greaseskids 122. In some instances, the grease pumps 60 are pneumatic pumpsdriven by an air supply 136, which may include an air compressor and airmanifold positioned within the safe zone.

The HMI control 130 may include a user interface with a configurationpage to configure (e.g., map) and validate grease supply connectionsbetween grease ports 54 of the trees 30 and outlets of the grease skid122. The user interface of the HMI control 130 may show (e.g., via adisplay 85) a screen depicting statuses of valves or greasingoperations. When a grease pump 60 begins to stroke, the number ofstrokes may be counted and displayed on the HMI user interface alongwith the amount of grease delivered for each greasing instance. Theamount of grease may be calculated from the number of strokes, from agrease meter, from a grease reservoir level sensor, from weighing agrease reservoir 58 supplying the grease (with the weight falling inproportion to the amount of grease drawn), or in any other suitablemanner. Total grease used for a job may similarly be determined anddisplayed to a user. Outlet pressures of the grease pumps 56 and inletand outlet pressures of the grease valves 64 may also be measured (e.g.,via pressure sensors 86) and displayed to a user to facilitate userdecision-making on greasing or valve control. Measurements and otherdata provided to the HMI control 130 may be stored locally ortransmitted to remote systems via network 134.

Although a few embodiments of the disclosure have been described indetail above, those of ordinary skill in the art will readily appreciatethat many modifications are possible without materially departing fromthe teachings of this disclosure. Accordingly, such modifications areintended to be included within the scope of this disclosure as definedin the claims.

What is claimed is:
 1. A system for use in a well application,comprising: a well tree having a flow cross and a plurality of valvesections coupled to the flow cross, the plurality of valve sectionscomprising actuatable valves, each actuatable valve having a grease portthrough which grease may be received to flush debris from the actuatablevalve; a greasing system having a grease reservoir, a grease pump whichis fed by grease from the grease reservoir, and a grease distributionnetwork connected between the grease pump and the grease ports, thegrease distribution network comprising a plurality of grease valvesactuatable to control flow of grease to selected grease ports; a controlsystem connected to the grease valves to selectively open and close thegrease valves; and a sensor system to sense valve position of eachactuatable valve, the sensor system coupled to the control system toprovide an indication to the control system when valve actuation isaffected by debris in a given actuatable valve.
 2. The system as recitedin claim 1, wherein the grease valves are disposed in a greasedistribution manifold.
 3. The system as recited in claim 1, wherein thegrease valves comprise a dedicated grease valve in fluid communicationwith each grease port.
 4. The system as recited in claim 1, wherein eachactuatable valve has at least a pair of grease ports.
 5. The system asrecited in claim 1, wherein the greasing system comprises dual greasereservoirs and dual grease pumps.
 6. The system as recited in claim 1,wherein the control system is configured to automatically initiateflushing of the given actuatable valve with grease to clear the debris.7. The system as recited in claim 1, wherein the actuatable valves arehydraulically actuatable valves.
 8. A system, comprising: a frac treehaving a plurality of actuatable valves; a greasing system coupled tothe plurality of actuatable valves to supply grease under pressure forcleaning debris from selected actuatable valves of the plurality ofactuatable valves; a valve control system to control actuation ofindividual actuatable valves between closed and open positions; a sensorsystem to sense valve position of each actuatable valve, the sensorsystem coupled to the valve control system to provide an indication tothe control system when valve actuation is affected by debris in a givenactuatable valve; and a greasing control system to automatically controlgreasing of individual actuatable valves.
 9. The system as recited inclaim 8, wherein the plurality of actuatable valves is positioned alongvalve sections coupled with a flow cross of the frac tree.
 10. Thesystem as recited in claim 8, wherein the plurality of actuatable valvescomprises grease ports with each actuatable valve having at least onegrease port.
 11. The system as recited in claim 10, wherein the greasingsystem comprises a plurality of grease valves positioned to selectivelycontrol flow of grease to the grease ports.
 12. The system as recited inclaim 11, wherein the greasing control system is coupled with theplurality of grease valves to enable control of selected individualgrease valves.
 13. The system as recited in claim 12, wherein the greasevalves are positioned in a manifold.
 14. The system as recited in claim12, wherein the plurality of grease valves is located at the frac treeand just one grease line is connected between the frac tree and a greasesupply.
 15. The system as recited in claim 12, wherein multiple greasevalves of the plurality of grease valves are daisy-chained together. 16.The system as recited in claim 8, wherein the valve control system andthe greasing control system are part of the same computer controlsystem.
 17. The system as recited in claim 8, wherein the valve controlsystem and the greasing control system are each part of a separatecomputer control system.
 18. A method, comprising: pumping grease to awell tree to remove debris from actuatable valves positioned in the welltree; providing grease valves along flows of grease to individualactuatable valves; sensing actuation of the actuatable valves todetermine which actuatable valves would benefit from greasing and debrisremoval; and using a greasing control system to selectively open greasevalves to accommodate desired debris removal from selected actuatablevalves.
 19. The method as recited in claim 18, further comprising usingthe greasing control system to automatically direct grease to specificactuatable valves based on feedback from a sensor system.